Monday, May 26. 2008

When installing Fedora 9 onto a system which already has a Fedora installation, it can be hard to decide whether to do an upgrade or a full reinstallation. Doing an update preserves virtually all of you data and settings, but doing a reinstallation gives a completely clean slate (at the expense of your data -- even if you use a separate /home filesystem, there are often system settings, web sites, and other data in /etc and /var).

Fortunately, when using logical volume management (the default storage scheme in Fedora), you can choose a middle ground: install the new version of Fedora onto a different logical volume without disturbing the existing LVs. The technique is simple:

3. On the custom layout screen, double-click on your main volume group (named VolGroup00 if you used the default VG naming scheme during the previous Fedora instllation).

4. Select each of our previous filesystems and create a custom mountpoint for each (for example, if you had just one LV filesystem -- the root one, from Fedora 8 -- you may want to mount it as /f8root). Do not format these filesystems. If you have filesystems such as a home that you wish to use, specify the appropriate mountpoint for each (e.g., /home).

5. Create a new logical volume to hold the new root filesystem. Give it a descriptive name such as "f9root" and specify / as the mountpoint. 10 GB is a reasonable minimum size for this filesystem (you can go as small as 4 GB). If you don't already have a /home filesystem, consider creating one in a logical volume to make upgrading easier next time.

6. Click Ok in the Edit LVM Volume Group window to close it. Double-click on your old /boot partition and specify /boot as the mountpoint (consider formatting this partition).

7. Proceed with the installation as usual.

One the system has been fully installed, you can simply copy any needed file from your old system (/f8root) to your new system (/). Once you're certain that you don't need the old filesystem any more, you can remove it (and again, system-config-lvm provides a simple way to do this graphically).

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